Voltage regulator for electron discharge devices



July 23, 1946. R. B. DOME VOLTAGE'REGULATOR FOR ELECTRON DISCHARGEDEVICES Filed Jan. 23, 1943 Inventor Robert B. Dome,

is Attorney.

Patented July 23, 1946 VOLTAGE REGULATOR FOR ELECTRON v DISCHARGEDEVICES Robert B. Dome, Bridgeport, Conni, assignor to General ElectricCompany, a corporation of New York Application January 23, 1943, SerialNo. 473,362

My invention relates to apparatus for the regulation of voltages appliedto electron discharge devices, and particularly to apparatus forregulating the voltage applied between the anode and cathode of electrondischarge devices of the cathode ray type.

In circuits employing electron discharge devices, such as cathode raytubes, a relatively high voltage is applied between the anode andcathode of the device, and it is desirable to maintain this voltageconstant. In apparatus such'as-oscilloscopes and television camera andreproducing devices, voltages derived from a common source arefrequently applied to the deflection plates as well as to theanode-cathode circuit so that variations in the deflection voltage areproportional to variations in the anode cathode voltage. The intensityof the electron beam in a cathode ray tube may be controlled by avoltage applied to a grid or control element. For example, this voltagemay represent changes in intensity of light in a picture or scene whichis being reproduced, and changes in voltage between the anode andcathode circuit may result from resulting changes in the load on thecathode ray tube. It is, therefore, desirable to provide somearrangement for preventing variations in the anode voltage caused bychanges in the anode current. In many cases it may be desirable tocompensate for changes in voltage due to changes in load current, butnot to regulate the anode voltage to prevent changes due to variationsin th voltage of the common source from which the anode voltage anddeflection voltages are derived.

It is an object of my invention to provide an tions in the currentflowing in the anode-cathode circuit.

The features of my invention which I believe to be novel are set forthwith particularity in the appended claims. My invention itself, however,both as to its organization and method of operation, together withfurther objects and advantages thereof, may best be understood byreference to the following description taken in connection with theaccompanying drawing, in which Fig. 1 is a circuit diagram illustratingschematically a portion of a television receiving appa- 6Claims.((1315-14) 7 ratus embodying my invention, and Fig. 2 is a cir-'- cuitdiagram illustrating a modification ofa. part of the circuit of Fig. l.1

Referring now to Fig. 1, the apparatus includes an electron dischargedevice III of the cathode ray type, which includes an anode II, acathode 12, a control electrode l3 and horizontal and ver-' ticaldeflection plates or members I4 and i5,-re:--

spectively. The device I 0 as illustrated is the picture tube or thetelevision receiver, a voltage corresponding tothe picture or-videosignalbeing applied to the grid l3 across a resistor Hi from a suitablesource, not shown, coupled" to the re sistor through a condenser l1.Direct current voltages for supplying the anode voltage and de-'-flection voltages of the devic I 0 are derived from a suitablealternating current supply, not shown,

coupled to a primary 20 of a transformer 2L A 7 high direct currentvoltage is applied between the anode II and the cathode l2 and isderived from a secondary winding 22 of the transformer 2! through ahalf-wave rectifier comprising a two-electrode electron discharge device23, and the usual smoothing condenser 24 connected be tween the cathode25 of the device 23 and ground, the device 23 having an anode 26connected to the secondary 22 One of'each pair of deflection plates I4and I5 is also connected to'the cathode 25 in accordance with the usualpractice. The deflection voltages for the vertical and horizontal platesl4 and I5 are derived from a full-wave rectifier 21. This rectifierincludes a secondary winding 28 of the transformer 2 i, and an electrondischarge deViceZB having anodes or plates 30 and 3i connected toopposite ends of the secondary 28, the center point of the secondarybeing connected to ground. The device 29 is provided with a cathode 32,which comprises a filamentor heater connected across a secondary 33ofthe transformer 2|, and the rectifier 21 also comprises a smoothingfilter including condensers 34 and 35 connected between ground andeither end of a choke coil 36, and the direct current voltage pro ducedby the rectifier is applied to vertical and horizontal deflectionvoltage generators and 4|, respectively, the rectifier being coupled tothe generators through a resistor 43 and a condenser 44. The verticaldeflection voltage'generator 40 across terminals 41. The generator 40 iscoupled to the plates I through a condenser 48, and the generator 4| iscoupled to the plates 1 4 through a condenser 49.

During the operation of the cathode ray device ID the load currentflowing between the anode H and cathode l2 varies and tends to producechanges in the voltage between the anode and cathode. In order toprevent changes in voltage due to the changes in the load current in thecathode ray device, an electron discharge device 52 is connected inparallel with the device I0 between the anode H and cathode l2. Thedevice 52 includes an anode 53 connected to. the

anode II, a cathode 54 connected to groundthrough a resistance 55, and acontrol electrode 56 connected to an intermediate point of theresistance 55. The resistance 55 is connected between the output of therectifier 21 and ground,- and the voltage drop in. the resistor 55therefore varies with the voltage of the rectifier. Consequently,.thechanges in drop across the resistor 55 follow change in the voltage ofthe source applied to the primary 20. The bias on the control electrode56, therefore, change with changes in the voltage of the source and isproportional tov corresponding changes in the deflection voltages. andin the anode voltage of the device it. The bias voltage of the grid 56is selected so that under the most severe load conditions, when thecurrent flowing through the device I!) is at its highest value, a verylow current in the vicinity of the cut-ofi value flows through thedevice 52. During the operation of the apparatus, when the device I0draws less current than the maximum value, the device 52 draws morecurrent and, as a result, the voltage across the parallel circuitincluding the anode l I and the cathode 12 of the device l0 does notrise appreciably. Since the bias voltage on the control electrode 56varies with the direct current voltage applied to the anodes H and 53,as a result of line voltage changes at primary 20, the device 52 doesnot regulate for changes in the applied anode voltage because thecut-off point of the device 52 moves in direct proportion to the changein the applied voltage and but little increase in current through thedevice 52 results.

Should it be desired to regulate both for changes in load current in thecathode ray device and for changes in the applied voltage derived fromthe source connected to the primary 20, the circuit of Fig. 1 may bechanged in accordance with Fig. 2 which illustrates the portion of thecircuit of Fig. 1. including the device 52 and the filter condensers andinductance of the rectifier 21. Corresponding elements of Flg. 2 aredesignated by the same numerals as in Fig. 1. The resistance 55 of Fig.1 is replaced in Fig. 2 by a resistance 58 connected between the cathode54 and ground, but not connected to the direct current supply from therectifier 21. A constant voltage device 59 is connected acrossresistance 58. The device 59 may, for example, be a neon tube whichmaintains substantially constant voltage over a wide range of currentflowing therethrough. The point at which the control electrode 56 isconnected to the resistance 58 is selected, so that, at the lowestvoltage applied to the anode II and at the greatest load current, thedevice 52 is biased almost to cut-off and draws very low current. Then,as the voltage rises across the device 52, a larger current will bedrawn thereby, and since the bias on the grid 56 is maintainedsubstantially constant by 4 the device 59, the current drawn by thedevice 52 compensates for changes in voltage regardless of whether theyare due to changes in load cur rent or in applied voltage, or both.

It will be evident that my invention provides a simple and effectivearrangement for regulating the voltage applied across an electrondischarge device, such as acathode ray tube so that the applied voltageis not varied by changes in load current. As an example, by way ofillustration. only, and not by way of limitation, a satisfactoryregulator embodying my invention, and which would be suitable for thecircuit of Fig. 1, may be provided by employing a 6F5GT tube as thedevice 52 with a resistance 55 having a value of 10,000 ohms. Thisregulator was employed with aload circuit at a potential of 2500 voltand this voltage was maintained substantially constant over a wide rangeof load currents.

Although I have illustrated one embodiment of my invention in connectionwith a television receiver, other applications will readily be apparentto those skilled in the art.. Therefore, it will be appreciated that Ido. not wish to be limited to the particular embodiment of my inventiondisclosed herein, and I contemplate by the appended claims to coverall-modifications-which fall within the spirit. and scope. of myinvention;

What I claim as new and desire to secure by Letters Patent of theUnited' States is:

1. In combination, a first electron discharge device having an anode, acathode and a control electrode, a source of voltage connectedbetweensaid anode and said cathode, and-means fonpreventing changes in thevoltage between said. anode and said cathode due to changes in'thecurrent flowing therebetween, said means including a second electrondischarge device connectedin parallel with the anode to cathode path of.said first device and having an anode and acathode and a controlelectrode, said means alsov including means connected in the cathodecircuit of said second device for providing a predetermined bias on saidcontrol electrode of said second device whereby current flows throughsaid second device to'compensate for changes in current flowing betweenthe anode and. cathode of said first device.

2. In combination, a first electron discharge device having an anode anda cathode and a control electrode, a source of voltage connected betweensaid anode and said cathode, and means for preventing changes in thevoltage between said anode and said cathode due to changes in thecurrent flowing therebetween, said means including a second electrondischarge device connected in parallel with the anode to cathode path ofsaid first device and having an anode and a cathode and a controlelectrode, said means also including a constant voltage device connectedin the cathode circuit of said second device for providing apredetermined substantially constant bias on said control electrode ofsaid secondv device whereby current fiowsthrough said seconddevice tocompensate for changes in current flowing between said anode and cathodeof said first device and to maintain the voltage between said anode andcathode of said first device substantially constant regardless ofvariations in the voltage of said source.

3. In combination, afirst electron discharge devic having an anode anda-cathode and a control electrode, a source of voltage connected betweensaid anode and said cathode; and means for preventing changes in thevoltage between said anode and said cathode due to changes in thecurrent flowing therebetween, said means including a second electrondischarge device connected in parallel with the anode to cathode path ofsaid first device and having an anod and a cathode and a controlelectrode, said means also including means connected in the cathodecircuit of said second device to produce a voltage varying in accordancewith the voltage of said source for providing a predetermined bias onsaid control electrode of said second device whereby th voltage acrosssaid second device varies with the voltage of said source but isindependent of variations due to changes in current flowing through saidfirst device.

4. In combination, a cathode ray device having a cathode and a controlelectrode and an anode and deflection members, a source of variablevoltage, means energized from said source for supplying deflectingvoltage to said deflection members and for supplying anode voltagebetween said cathode and said anode whereby said deflecting and anodevoltages tend to be subject to variation in the voltage of said source,means for preventing changes in the voltage between said anode and saidcathode due to changes in the current flowing therebetween, and meansassociated with said last mentioned means for effecting operationthereof to prevent changes of voltage at said deflecting members and atsaid anode due to variations in the voltage of said source.

5. In combination, a cathode ray device having a cathode and a controlelectrode and an anode and deflection members, a source of variablevoltage, means energized from said source for supplying deflectingvoltage to said deflection members and for supplying anode voltagebetween said cathode and said anode whereby said deflecting and anodevoltages are subject to variations in the voltage of said source, andmeans for preventing changes in the voltage between said anode and saidcathode due to changes in the current flowing therebetween, said lastmentioned means including an electron discharge device having an anodeand a cathode and a control electrode and connected between the anodeand cathod of said cathode my device, said last mentioned means alsoincluding means connected in the cathode circuit of said electrondischarge device for providing a predetermined bias on the controlelectrode thereof whereby current flows through said electron dischargedevice to compensate for changes in current flowing between the anodeand cathode of said cathode ray device.

6. In combination, a cathode ray device having a cathode and an anodeand a control electrode and vertical and horizontal deflection members,a source of variable voltage, means energized from said source forsupplying deflecting voltages to said deflection members and forsupplying anode voltage between said cathode and said anode whereby saiddeflecting and anode voltages are subject to variations in the voltageof said source, and means for preventing changes in the voltage betweensaid anode and said cathode due to changes in the current flowingtherebetween, said last mentioned means including an electron dischargedevice having an anode and a cathode and a control electrode andconnected between the anode and cathode of said cathode ray device, saidlast mentioned means also including a voltage supply connected in thecathode circuit of said electron discharge device and subject to thevariations in the voltage of said source for providing a bias on thecontrol electrode thereof whereby current flows through said electrondischarge device to compensate solely for changes in current flowingbetween the anode and cathode of said cathode ray device.

ROBERT B. DOME.

